Every meeting I've ever had since I began full-time advocacy, I have brought with me a book of Seamus Heaney's poems. I always think if you're asking somebody for something it's a good idea to give them something first.

So I always gave them Seamus Heaney's poems. This is from the Pope to every president I have ever met. In this past week I gave Seamus' book Electric Light to President Johnson Sirleaf in Liberia. She's currently obsessed with the efforts to bring electricity to her people so she could not believe it.

Seamus has been with me on every journey I have taken, and there have been many times when a retreat into his words has kept me afloat.

Most of our life in this kind of work is very concrete, full of facts, but we all have to seek redress from time to time in poetry. Seamus was where I went for that. He was the quietest storm that ever blew into town.

As an activist, From the Republic of Conscience has been like a bible for me, something I return to and have returned to for as long as I can remember. Some of those phrases are like tattoos for me, worn very close to the heart.

Singer songwriter Paul Simon:

I was in the audience at the Abbey Theatre in Dublin on June 9, 1991, when Seamus Heaney read from his new book of poems Seeing Things.

I know the exact date because he kindly inscribed his book for me and dated it. But I wouldn't have forgotten that night, with or without the month and year.

Seamus gave a mesmerising, witty and emotional performance, and it was a rare opportunity for me to hear the sound of his words spoken with their true accent.

Popular culture likes to house songwriters and poets under the same roof, but we are not the close family that some imagine. Poets are distant cousins at most, and labour under a distinctly different set of rules. Songwriters have melody, instrumentation and rhythm to colour their work and give it power; poets accomplish it all with words.

Seamus, though, was one of those rare poets whose writing evokes music: the fiddles, pipes and penny-whistles of his Northern Irish culture and upbringing.

It's frustrating to try to capture even a glimpse of the man, his verbal virtuosity, his wit and Irish charm. Recovering from a stroke in the hospital, he greeted his friend and fellow poet Paul Muldoon with, "Hello, different strokes for different folks."

I admire the directness and simplicity of his work, a virtue most writers aspire to but rarely achieve. Seamus and I met through our mutual friend Derek Walcott. I visited him in his home outside Dublin, and we continued our conversations at my place in Manhattan.

Obviously, I'm a fan even more of the man than the poetry, though there are few poets I would rank as his equal.

Snow Patrol frontman Gary Lightbody:

School was that place I got the bus to every day and got to play sports some days in the afternoons and not much more. Then Mark McKee started working as an English teacher and brought with him three secret weapons. The works of Van Morrison, Bob Dylan and one Mr Seamus Heaney.

Yes, the day he arrived at the school would change my life but as I say I didn't know it yet. As Mr McKee began to read from the little volume of poetry in his hand I found myself, for the first time that day, maybe that week (sorry mum, this will all be news to you), actually listening ... Mr McKee was reading Digging by Seamus Heaney and I was hooked. I devoured the volume Death of a Naturalist then North, then Station Island, the lot. Seamus Heaney made me want to be a writer.

I wrote poetry every day and was published at 15, many times. All of it terrible and I have to read it now, if I ever do, from behind splayed fingers, but it started me on the path that would take me to here, sitting in California writing Snow Patrol's seventh album after a 20-year career that has taken me around the world many times and shown me things I never dreamed of.

There are people, as my friend Gabrielle is fond of saying, that are part of an 'invisible tribe'. Artists and writers that touch people on a level that beds deeper into our souls and hearts.

People of profound light, love and kindness that simply and maybe even without their knowledge make us and the world around them better. Stephen Fry is one. Guy Garvey another.

To see them on the stage, screen or on the page makes us feel safer, happier, stronger, more centred and less confused by life and what the hell we're doing here.